U.S. Pat. No. 4,924,738 of Hue N. Che disloses a bar puller having adjustable jaws which comprise fingers made of a resilient material; a similar device is also disclosed in U.S. Pat. No. 5,046,226 of Hue N. Che. The fingers of the Che device, which are resilient spring arms, extend forward from a housing adapted to be mounted at a tool station of a computer numerically controlled lathe having a turret.
The device of the Che patent must be engaged by pushing it onto the end of a bar with a substantial amount of force; and a substantial amount of pressure is also required to disengage the bar from the Che device. Although this is not a problem with the relatively large numerically controlled lathes used in prior years, the newer CNC lathes are substantially smaller and less tolerant of repeated applications of such force.
Furthermore, in spite of the multiplicity of fingers used in the device of the Che patent, the gripping force of such device depends upon the amount of spring pressure in the resilient arms of the device which, in most applications, is limited to a relatively low pressure.
It is an object of this invention to provide a bar puller which can be engaged and disengaged with only a minimal amount of force and which exerts a gripping force substantially greater than the gripping forces previously available.